E. JUSTIFICATION This SRC is designed to assist investigators with the identification and recruitment of adequate samples of research participants and is particularly helpful in facilitating the study of large samples of selected disorders. The SRC serves as a centralized source for research subjects in a geographic area with numerous investigators studying the same disorders. Currently, the SRC has data on 4,600 potential subjects and is assisting approximately 15-18 projects annually. Two important goals of the Registry are the conservation of research subjects by limiting inappropriate contacts (subjects who do not match research requirements are not contacted) and timely and cost effective recruitment of research participants who are considering participating in research. Another goal of the SRC is to avoid attrition of subjects by contacting families annually to update addresses and phone numbers. An overarching goal of the SRC is to populate our registries with large numbers of appropriate research participants and to provide sufficient characterization for researchers to identify subgroups of interest. Web and computer database technology makes it easy for researchers to identify and access samples of interest.